Post by: Mike Babcock on January 03, 2005, 01:36:54 PM
I was contracted to do an in the round show with a major "A" level act in a large NHL Hockey arena for a high brow New Years Eve party. That is as specific as I will put it, since the names are meaningless in this thread and if you want to know you can search the internet.
I'm going to backtrack for a second. About a month ago I attended a seminar taught by Mauricio Ramirez of Meyer Sound. In this seminar we were told the theories behind line array systems (subs included) and included in this was a whole section on cardioid subs. This seminar used a program called MAPP and if anyone knows it, knows it's advantages. So using MAPP at the seminar I saw sound in a light I have never quite seen it before. Things I have heard with my own two ears are visually shown on the screen backed up by explanations by Mauricio as to why it is how it is. I do not have any Meyer products in house, yet, but the theories used in MAPP can be translated to similar boxes. If anyone doesn't know, I have a fairly sizable EAW 850 inventory and not much else. But even that fact doesn't matter with the issues here.
So while preparing myself for this show I decided to use MAPP to, well, map out my rig placement, figure out how many of my boxes would cover well, find out what I would need for frontfill, etc. The problems started happening when I got to sub placement. This sub placement was how my boss wanted it. Below is my MAPP screenshot showing what I started with:
http://www.themonitorguy.com/pics/albums/userpics/10001/nonc ardioidmapp.jpg
As you can see, the dark red areas have the most energy at 63 hz going to the least energy with the blue coloration. Plainly, it would have been unacceptable to have more sub energy on the stage than in the crowd. Add in the fact that the bass player for the band stands dead center and plays an acoustic bass, the FOH guy for the band would have had no end of troubles there. Flying the subs was not an option, though it would have been preferrable IMO.
So when I saw that, I started thinking about how to do a cardioid sub pattern to reduce that energy on the stage. And with the help of fellow labster Harry Brill through IMs and transferring MAPP files back and forth, and other useful insight from Phill Graham and David Buehler, we ended up with the following:
http://www.themonitorguy.com/pics/albums/userpics/10001/card ioidmapp.jpg
The top and bottom subs were reduced 4db in the program to simulate the area of coverage, long throw front and back, short throw to the sides. You can plainly see that the coverage was nice and even throughout with lots of cancellation on the deck. This was exactly what I was looking for, I made my case to the boss and was awarded with a "hmm, I never thought of that, go ahead" answer. Now comes reality...
Due to placement of monitor world and three guitar tech lands, I could not deploy the subs exactly how I wanted to, evenly spaced around the entire stage. So I had to adjust to a cardioid pattern of 4 wide in each corner. I do not have a MAPP of that pattern (maybe Harry can help us with that
), but it acheived much the same result with a couple of cancellation lobes and power alleys. But all in all, much, much, much better than how I was originally told it was going to go. The following is a fairly dark picture of one of the sub arrays.
http://www.themonitorguy.com/pics/albums/userpics/10001/subl ineSPTF2.jpg
I needed to perform the following demo for each of the techs that showed up with the band. Have them sit center stage and I turn on the inner row only of subs and have them listen, then turn the outer row of subs on and have them listen to the entire sub array. Every single one of them thought I was muting something and had to be verified by their FOH guy actually muting and un-muting to prove to them I wasn't using any mirrors of any kind. The sub cancellation on the deck was amazing and certainly worth any additional amount of time I had to take to deal with it. The band is used to traveleing with M3D subs so they do not normally have to deal with this issue.
Here's a shot of the entire rig, sorry for the graininess, camera phones kind of suck:
http://www.themonitorguy.com/pics/albums/userpics/10001/SPTF rig.jpg
So in closing, learn what you can about doing audio if you are serious about it. This cardioid sub thing is not a new invention, and not tough to deploy, it's been around for quite some time. Even line array is not a new idea. Throwing up a bunch of boxes and saying 'close enough for rock 'n roll' is fine if you don't care. Figuring out ahead of time which tools are required is the key here. Line arrays are not always the best solution, but sometimes are. The more knowlege you have means more tools in your toolkit. Go to the Meyer seminars, join SAC, learn Smaart, go to Doug and Scovills seminar. Every little detail can and will count. Even after 15 years now, I still try to learn something new every day. Man, has it been 15 years already
Mike
PS: Dave, if any of the pictures are too big, let me know and I'll trim em back, or just leave links.
Post by: Aaron Lane on January 03, 2005, 02:22:39 PM
Info like this is why I read this board.
Aaron Lane
Post by: Phillip_Graham on January 03, 2005, 03:23:40 PM
| Quote: |
So when I saw that, I started thinking about how to do a cardioid sub pattern to reduce that energy on the stage. And with the help of fellow labster Harry Brill through IMs and transferring MAPP files back and forth, and other useful insight from Phill Graham and David Buehler, we ended up with the following: |
For those unfamiliar with MAPP, it is a Java applet you have to sign up for at Meyersound. You design arrays in the local applet, and then a supercomputer cluster at Meyersound calculates the array's response. Array files are stored in XML, and can be sent to other users. It's sort of like a more powerful version of EV's Arrayshow or RACE.
FWIW, My original suggestion to Mike was a T-shaped flow array of SB850's in the middle of the main 850 cluster. I think the cardiod arrangement was a very clever "boss approved" arrangement.
http://www.turnofthecentury.net/sublineSPTF.jpg
For those unfamiliar with the "cardiod sub" technique, let me explain what is done processing-wise. The rear row of subwoofers is delayed to line up with the spill from the front ones. The rear boxes have inverted polarity. The result is that the waves cancel in behind the two rows of boxes, and sum coherently in front. The wavelength of maximum cancellation is a function of the front-to-back driver spacing. The longer the spacing, the lower the frequency.
Mike also could have placed the two subs back to back (i.e. speakon to speakon) and then delayed the front boxes. Or if the box was deep, like a SB1000, he could have stacked them vertically, turning every other one facing backwards, then apply the delay.
The effect is analagous to allowing some sound leak to the rear of a microphone diaphragm via the porting on a cardiod microphone.
You can do even fancier patterns than mike's but this is a good example to grasp the basics.
This technique also works in other configurations. In your narrow "shoebox" proscenium soft-seater, you can do a horizontal line array of subwoofers across the front of the stage area to eliminate power alley, and then do a second line of subs, like mike has done, to keep the energy from spilling off the back of the subs onto the stage.
Edit: I was going to draw the above in MAPP as an example, but it appears that past LAB-rat Harry Brill already did it for me. Please see the attached PDF file for pictures of a horizontal sub line array+cardiod model.
Post by: Rex Ray on January 03, 2005, 04:38:41 PM
Rex(useta mix Kenny Rogers in tha round) Ray
Post by: John Chiara on January 03, 2005, 04:40:27 PM
| gtphill wrote on Mon, 03 January 2005 20:23 |
This technique also works in other configurations. In your narrow "shoebox" proscenium soft-seater, you can do a horizontal line array of subwoofers across the front of the stage area to eliminate power alley, and then do a second line of subs, like mike has done, to keep the energy from spilling off the back of the subs onto the stage. |
Or buy a bunch of SPL BDeaps!.
Post by: Jason McLaurin on January 03, 2005, 04:50:18 PM
Great case study.
I did an almost identical show on new year's eve, arrayed like your "bad" example. My mon beach was right in that dark red spot behind a corner array... talk about getting your bell rung. There's nothing like spending the first 10 seconds of 2005 chasing down RF's so that they don't drive off the rink in the rappers' Mercedes
Have you done any of the same modeling for standard ampitheatre / end stage setups? I wonder if that technique would still be worthwhile when the performers aren't directly behind the subs.
-Jason
Post by: Chris Cowley on January 03, 2005, 04:56:17 PM
Post by: Owen Orzack on January 03, 2005, 05:02:31 PM
If you are able to have a simple way to do it (such as with a DSP contolled amplifier) you can do it on tour, every day with great results.
http://www.dbaudio.com/pub/files/TI330.PDF
Post by: Phillip_Graham on January 03, 2005, 05:04:48 PM
| Jason wrote on Mon, 03 January 2005 16:50 |
Hi Mike, Great case study. I did an almost identical show on new year's eve, arrayed like your "bad" example. My mon beach was right in that dark red spot behind a corner array... talk about getting your bell rung. There's nothing like spending the first 10 seconds of 2005 chasing down RF's so that they don't drive off the rink in the rappers' Mercedes Have you done any of the same modeling for standard ampitheatre / end stage setups? I wonder if that technique would still be worthwhile when the performers aren't directly behind the subs. -Jason |
Jason,
There's always an advantage to using it, namely increasing the amount of sound in the forward lobe. Since energy is conserved, all the energy that would normally be spilling away is focused into the main audience. A typical standard sub setup "wastes" close to half the energy due to spill behind the stage. This puts (some of) that sub energy into the audience, giving you more headroom.
Also, you may find the reduced low end wash on stage will allow for lower monitor levels, or not.
It won't fix power alley issues, for that you still need center clusters, horizontal line arrays, distributed clusters, or delay shading. You can combine the cardiod subwoofer technique with these other techniques to work on both issues.
Post by: Guest on January 03, 2005, 10:02:54 PM
Post by: Guest on January 03, 2005, 11:14:52 PM
Post by: Mike Babcock on January 03, 2005, 11:27:40 PM
If one had the space, they can add more sub lines, 3 deep, 4 deep, etc and have more cancellation in back and more addition out front. It will also give a wider frequency range of add and cut because there is more than one spacing between boxes affecting a different frequencies. In theory the first delayed line reduces the fundamental frequency, the next line cuts the fundamental frequency plus the frequency half that (or twice the wavelength) and so on.
Work is fun again
Mike
Post by: A Man on January 04, 2005, 01:21:18 AM
You'll have to give me a tutorial of MAPP when we get a chance.
Even though I had the luxury of flown subs, it looks like this would have been a good thing if it was implemented at NEC-Birmingham or that London show we did.
Great job guys!!
Post by: Josh Evans on January 04, 2005, 11:48:55 AM
"Mike also could have placed the two subs back to back (i.e. speakon to speakon) and then delayed the front boxes. Or if the box was deep, like a SB1000, he could have stacked them vertically, turning every other one facing backwards, then apply the delay."
I like this approach better than the others, for rigging, and for keeping the polarity consistent.
The BDEAP-32 (afaik) isnt really a flyable box, meaning youd probly have to add tracks to it. I only know of one job where they have been flown, and dont remmeber much about it.
Just so yall know
http://www.ada-acousticdesign.de/english/e_online/index_onli ne.html
http://www.ada-acousticdesign.de/EaseMapsonline/EaseOnline1. aspx
EASE online can do the exact same thing as MAPP, and more!
and dont forget.
http://www.ifbsoft.de/
FREE demo!!!
The thing to keep inmind is that with some of them youll have to use higher frequencies and scale them down. This is because acoustical prediction programs dont do very well with frequencies bellow 100Hz. Theres way too many variables!
Post by: Mike Babcock on January 04, 2005, 09:15:07 PM
If anyone has any questions or comments, I would love to hear them.
Mike
Post by: Tom Reid on January 04, 2005, 09:25:53 PM
Can I ask, when you fly subs, what do you need to deal with as far as the "Z" axis? How does cardiod work "up there"?
Post by: Mike Babcock on January 04, 2005, 10:03:49 PM
| Tom Reid wrote on Tue, 04 January 2005 21:25 |
I'm following this thread, and I think I've absorbed about %90 of it. Can I ask, when you fly subs, what do you need to deal with as far as the "Z" axis? How does cardiod work "up there"? |
It works just like a single cardioid pair. I have attached yet another MAPP shot for you.
The only problem I have with MAPP is that it gives you 2 axis, it is not a 3-D modeling system, so you can look at it as length and width, or length and heigth, or any other combination of 2 axis. My original plots were as if looking down on the stage, the one in this post is as if looking at the stage, height and width (or length). The cardioid array will act as a cardioid array in all axis. If you look at the array from behind the box or directly in front of the box, it would look like a single sub, if you look at it from the top, bottom or either side it will have the same pattern, the pattern just gets wider as the array becomes wider, or taller as the array gets taller (depending on your perspective). Make sense yet?
Mike
Post by: Tom Reid on January 04, 2005, 10:08:00 PM
Yeah, that's what I was looking for, the lack of a 3D view.
One can assume the sub is going to play the same in the Z axis as the X axis I hope.
When you fly subs, can you get lost in the detail trying to point the null lobe down and back onto the stage?
Just a mental experiment. I don't think I'll be big enough to ever fly subs in my little corner of the world.
Post by: Guest on January 04, 2005, 10:32:57 PM
Post by: Eytan Gidron on January 05, 2005, 09:02:10 AM
| gtphill wrote on Mon, 03 January 2005 22:23 |
For those unfamiliar with the "cardiod sub" technique, let me explain what is done processing-wise. The rear row of subwoofers is delayed to line up with the spill from the front ones. The rear boxes have inverted polarity. The result is that the waves cancel in behind the two rows of boxes, and sum coherently in front. The wavelength of maximum cancellation is a function of the front-to-back driver spacing. The longer the spacing, the lower the frequency. |
Thanks Phill for this explenation. I am not sure that I got it right. Can you get a bit more specific - can you give an example with actual numbers (such as which delay time to which spacing, which frequencies will it affect?)
Will this method work well with horn loaded subs (such as the Turbo subs)?
Post by: Phillip_Graham on January 05, 2005, 09:32:23 AM
| Eytan Gidron wrote on Wed, 05 January 2005 09:02 |
Thanks Phill for this explenation. I am not sure that I got it right. Can you get a bit more specific - can you give an example with actual numbers (such as which delay time to which spacing, which frequencies will it affect?) Will this method work well with horn loaded subs (such as the Turbo subs)? |
Place both subs facing forwards, one behind the other. Space them 1/4 wavelength of the center frequency of the desired bandpass. Invert the polarity of the rear box, and then delay it the equivalent quarter wavelength time (i.e. .9ms/ft.).
Otherwise, process all the boxes the same, so that they have the same basic phase response (x.o. phase + acoustic phase).
Hopefully that's clearer.
Post by: Guest on January 05, 2005, 10:45:01 PM
Post by: Andy Leviss on January 06, 2005, 01:03:30 AM
| gtphill wrote on Mon, 03 January 2005 15:23 |
Mike also could have placed the two subs back to back (i.e. speakon to speakon) and then delayed the front boxes. DF file for pictures of a horizontal sub line array+cardiod model. |
I'm not sure I'm entirely following this. Why would you then delay the front ones instead of the back? Isn't turning the back box 180 degrees the same as reversing its polarity, once you account for the different spacing between the drivers from having them located on the other side of the box (which is just a factor of the delay setting, right?)?
Also, here's a real world question for those of you who have much more experience and knowlege of these sort of things than I do. I'm touring an arena show (typical end stage setup, with the stage about 2/3 back in a standard hockey arena, with the remaining 1/3 or so as backstage). There's a small ramp and a circular thrust stage that ends up just slightly off-center (yup, even Elmo gets an ego ramp ;o)
Being as it's a family show with tracked music and equipment is limited, they've got me out with a pair of Meyer USW-1s. Yup, just two.
The original rig had the subs one per side under the front edge of the stage, directly below the main array on each side. Needless to say, the power alley issues were less than desireable. Between that and a couple venues in a row where we couldn't fit the subs under the deck, I ended up moving the two subs to the center line under the thrust stage, and delaying them to align them with the main arrays, angling them out slightly to help cover the sides that the boxes were now on the side of/behind instead of in front of).
This has helped improve things a lot, so that there's now much more consistent low end throughout the venue (and at notably lower levels than I needed before), but I'm always on the lookout for a better solution (aside from adding more subs, which, while the best solution, isn't going to happen). Any thoughts?
I should add that if it is a viable solution for this situation (which I'm not sure it is, especially with only two boxes), cardioid is, unfortunately, also not an easy option, since the USWs require a speaker processor directly before the amps (and tied in after the amps to provide safety limiting), and I (of course) only have one processor, the split coming after the processor. If it really would help, I could try to make a case to the folks back at the office for a second processor if they have one at the shop, but I don't know how successful that would be.
Post by: Phillip_Graham on January 06, 2005, 03:06:47 PM
| Andy Leviss wrote on Thu, 06 January 2005 01:03 | ||
I'm not sure I'm entirely following this. Why would you then delay the front ones instead of the back? Isn't turning the back box 180 degrees the same as reversing its polarity, once you account for the different spacing between the drivers from having them located on the other side of the box (which is just a factor of the delay setting, right?)? |
Hey Andy,
[Edited after realizing I didn't need to second guess myself]
Actually, this a correct way of doing it.
Mike B's way:
You need to cancel the waves behind the front box. So (for simplicities sake) if the front box is producing cos(x) then the rear box needs to produce -cos(x + D) where D is the time it takes for the sound from the front box to reach the rear. The "-" comes from the polarity invert/box direction, and the D comes by delaying the rear box long enough from the sound from the front box to get there.
Alternative way:
Space the boxes 1/4 wavelength apart (90 degrees apart). Now delay the front box another 1/4 wavelength (90 degrees). The output from the the front box takes 1/4 wavelength to reach the rear box, and other 1/4 wavelength you added artificially, so cancellation ensues. The undelayed sound from the rear box takes 1/4 wavelength to get to the front box, so it sums in phase out front. Because sound diffracts around the rear box almost perfectly, it makes very little difference whether it is facing forwards or backwards, and you can't think of turning it around as a polarity inversion.
Note that the second method doesn't work as well as the first, because the individual box does provide some degree of forward directivity, and there is slightly less (3dB or so) less sound behind the box than in front. This leads to a more hypercardiod-like pattern, which can be mitigated by turning down the rear sub about 3dB. But, by turning down the rear sub 3dB you lose that energy in the main lobe:
Post by: William Mortensen on January 06, 2005, 08:46:59 PM
Also, for what it's worth, I kind of doubt that Meyer's (and Nexo's, for that matter) cardioid subs use a technique that's this simple, since it works best at only one frequency, and I doubt that Meyer would reveal one of their great secrets to you guys like that anyway.
They seem to have figured out how to do this on a broadband basis.WM
Post by: Guest on January 06, 2005, 10:22:55 PM
Post by: William Mortensen on January 06, 2005, 11:23:13 PM
| Harry wrote on Thu, 06 January 2005 19:22 |
I work for a Meyer house currently. |
I did not know that.
| Quote: |
They don't seem to have any issues with teaching anyone and everyone. What makes you think they are trying to hide anything? |
I didn't say they were. I was just saying that I didn't think that this technique was all there is to Meyer's cardioid LF technology, because I doubt that a company would invest years of R&D into perfecting something that no one else has done and then tell the world about it. And there is definitely more to the PSW-6 and M3D(-Sub) than this. Here's the entirety of a Q&A on the website about it:
| Quote: |
How does the M3D-Sub steer without digital delay? We use analog phase networks to control the cardioid behavior of the M3D and the M3D-Sub. |
Which is not the same thing as the (still very interesting and useful) technique that they have told us about through you, Mike, and Phill.
| Quote: |
I have also used the CD18s and CD12s. The CD12 uses EXACTLY this method, with perhaps a bit of frequency response shading to make up for the fact that the rear is facing back. This is not only good for 1 frequency either. The wavelengths are long. It works very well about an octave in each direction, see for yourself. |
That's good to know. I don't think anyone had mentioned what kind of bandwidth this technique is really effective over in this thread. I figured it was maybe an octave (total), and certainly less than two. But obviously I was wrong, so thank you for setting me straight on that.
| Quote: |
(The GEO T uses a similar method with a low pass filter that has a slope that works with the front speakers to add control as the frequency drops.) Back to Meyer. I don't know what the M3D and M3DSub are doing exactly, |
Right. Because they didn't tell you. And I wouldn't expect them, or any other company, to do so. That's all I was trying to say, Harry!
| Quote: |
but according to Mauricio it is not advantages to have rear firing drivers, except for the package and repeatability of an all in one box. The full benefits are only realized with all the boxes facing the same direction. This method with only 2 sources is not he best. A better method uses 4 sourced, spaced 1/4 wavelength of the highest frequency of interest, then delay 3 of them back to the one in the back. This method yields about a 23dB difference front to back. |
Okay. I believe I've read that the PSW-6, or the M3D, or something, can achieve even better directivity than that. Because it uses the aforementioned analog phase networks that Meyer most likely spent years developing. And that's what I was referring to when I said "great secrets"--I meant the kind of processing that they do, which again is apparently much more complicated than a simple delay.
| Quote: |
I find your attitude disturbing. I would be happy to pass Mauricio's phone number to you, and you can also speak with Dr. Don Pearson, whome I sat next to in the class. |
I'm sure they have much better things to do than talk to me. Honestly.
| Quote: |
Would that be proof enough for you that Meyer is interested in improving the quality of audio in the industry as a whole? |
Again, I didn't say they weren't. In fact I'm very impressed with the educational efforts (that they're touting on the front page of their website right now).
All I meant was that, while they are certainly making a huge effort to, as you say, "improve the quality of audio in the industry as a whole", obviously they're not going to give away their intellectual property for free, i.e. tell the world how their proprietary technologies work. I just didn't want anyone reading to get the idea that that's all their cardioid technologies are. Fact is, I have no idea what they are, and I doubt I could understand how they work.
Okay? I'm sorry if my post was less than clear. I wasn't trying to say anything particularly important. Just an idle thought.
WM
Post by: Phillip_Graham on January 06, 2005, 11:33:12 PM
| Quote: |
Okay? I'm sorry if my post was less than clear. I wasn't trying to say anything particularly important. Just an idle thought. WM |
Don't let Harry get to you. He misread the smirk in your post, and his post shouldn't be read as seriously as it seems. He's the first to admit he comes on too strong in print at times.
Back to the topic!
Post by: Peter Morris on January 07, 2005, 12:18:36 AM
This is all great stuff and it works …..
But, there are a few points to note:
It only works over a limited bandwidth, probably about an octave, so with the EAW subs operating 40 to 80hz and with the distances and delays based on a centre frequency of 60hz - no problems.
The impulse response is not perfect. Imagine if the waveform was a single pulse - the top half of a 60hz sine wave.
The front box will be producing sound for the equivalent of 180 degrees of time (at 60hz) before anything from the rear box is received. What is received (from the rear box) is inverted and delayed by 180 degrees equivalent of time.
So the original sound is the top half of a sine wave, but the received sound is a complete sine wave, the original plus a delayed and inverted original.
I guess you could call it distortion, it will still sound “nice” and could well be the best compromise in many situations. At back however every thing cancels perfectly.
Peter
Post by: Phillip_Graham on January 07, 2005, 12:47:53 AM
| Peter wrote on Fri, 07 January 2005 00:18 |
The impulse response is not perfect. Imagine if the waveform was a single pulse - the top half of a 60hz sine wave. The front box will be producing sound for the equivalent of 180 degrees of time (at 60hz) before anything from the rear box is received. What is received (from the rear box) is inverted and delayed by 180 degrees equivalent of time. So the original sound is the top half of a sine wave, but the received sound is a complete sine wave, the original plus a delayed and inverted original. I guess you could call it distortion, it will still sound “nice” and could well be the best compromise in many situations. At back however every thing cancels perfectly. Peter |
The impulse arguement is of little consequence at these frequencies, as the group delay incurred is of the order of magnitude of the crossover filters, the box tuning, etc. Plus, as you are well aware, the notion of anything "impulsive" in such a bandwidth limited system is a little nebulous.
The fact you get good summation for most of the space in front of the array is indicative of the relatively good phasor sum across a broad range of azimuths.
I feel any phase penalties incurred by such a setup, in the frequency region where most system phase issues lies anyway, is a good compromise to make relative to the mess of room acoustics/stage bleed issues in the low frequencies.
Post by: Peter Morris on January 07, 2005, 02:26:21 AM
I don’t disagree, but you do loose something. I often wonder if it’s easier to use a block of LAB subs or similar horns. A large block will have reasonable pattern control, none of the problems associated with ported boxes and the cardioid pattern control, not to mention way less second harmonic distortion smudging the low end of the vocals.
I would love to see some polar plots on a reasonable sized bock of LAB or EAW BH760 subs, then use MAPP to determine the best compromises for various situations and compare them to what you get with the various cardioid subs on the market.
Peter
Post by: jomarsh on January 07, 2005, 06:56:14 AM
| Quote: |
Also, for what it's worth, I kind of doubt that Meyer's (and Nexo's, for that matter) cardioid subs use a technique that's this simple, since it works best at only one frequency, and I doubt that Meyer would reveal one of their great secrets to you guys like that anyway. They seem to have figured out how to do this on a broadband basis. |
I found this web page that seems to suggest that it is simple (info about Meyer and Nexo is at bottom of the page). I was sceptical when I read it but after reading you guys I guess it is Ok. Can I assume that the rest of the page is accurate too?
Heres the page
http://burton-manor.co.uk/Audio/LAthoughts.htm
Thank you.
Joe
Post by: Mike Babcock on January 07, 2005, 11:31:06 AM
| William Mortensen wrote on Thu, 06 January 2005 20:46 |
Or do you guys have MAPP Online Professional? |
Yes, we have MAPP Online Pro, it was a prerequisite to going to the seminar. It is still in beta version, so I don't know how widely available they are willing to make it. I'm sure you could send Meyer an email requesting it.
Mike
Post by: Mike Pyle on January 07, 2005, 03:20:18 PM
| Harry wrote on Wed, 05 January 2005 19:45 |
Speed of sound at 70 Deg F 1129 60Hz center frequency. 1129/60/4 = 4.7 ft (Wavelength (f/cycle) = Speed of Sound / Frequency) Center to center (just measure front of cab to front of cab with both facing forward. 4.7ft is the spacing. 1000/60/4 = 4.17 (Period (ms) = 1000 / Frequency) Set the delay to the rear speaker to 4.17 and reverse the polarity. Keep in mind the speed of sound changes with temperature. |
If the distance between the boxes was increased to 1/2 wavelength instead of 1/4 with the corresponding delay added to the front box, and with the same polarity on the front and rear boxes (instead of reversed polarity), would the 2 subs still cancel each other?
I'm asking simply to know if other physical arrangements are workable if the situation demanded it.
Post by: Guest on January 08, 2005, 12:35:22 AM
Post by: Dan Mortensen on January 08, 2005, 03:46:20 AM
| Harry wrote on Thu, 06 January 2005 19:22 |
I find your attitude disturbing. I would be happy to pass Mauricio's phone number to you, and you can also speak with Dr. Don Pearson, whome I sat next to in the class. Would that be proof enough for you that Meyer is interested in improving the quality of audio in the industry as a whole? |
Hi Harry,
When the PSW-6 came out, it was the first commercially available cardioid subwoofer that functioned as well as it did. At that time, I spoke with someone within Meyer (not one of the main design engineers, I believe) who explained that the method was not simply reversing polarity and adding delay, because that method would only work at one frequency, and this worked for more than two octaves. Since I don't know any better, that explanation satisfied me.
The description in the operating instructions says
"The cardioid coverage pattern is created by a complex
electronic and geometric relationship between the four
drivers at the front of the cabinet and the two drivers at
the back of the cabinet."
What you and Mike are describing does not sound like something I would describe as "complex". Clever, yes, but not that complex, in the scheme of things. And I'm certainly not saying you're wrong.
You have experience that I don't have, and I don't have insight into how the things actually work. I can only parrot what I've been told and what I've read. And that was where Will got what he posted.
If Meyer's method is as complex as they say, and if they are proud of having the first successful commercially available product using what they figured out for the first time, I would not expect them to jump up and offer it free to anyone who would listen.
That has nothing to do with their interest in improving the quality of audio in the industry as a whole, but, as Will said, with protecting their intellectual property.
If everyone else has figured it out, then maybe there is no intellectual property left to protect, or perhaps they choose not to protect it, as with their patent of the trapezoidal design of loudspeaker enclosures. I don't know, and if their guys are giving it away, well, that says something.
Regardless, your reply came out definitely stronger than was pleasant to read, and I hope stronger than you intended. It was nice of Phil to put it in perspective.
Thank you.
Best wishes,
Dan
PS I'm glad you're with a Meyer house, and that you're part of the family.
Post by: KeithBroughton on January 08, 2005, 08:57:37 AM
I am going to try this cardioid method with some 2x14 JBL Array subs.
I'm very grateful for the info supplied here and many thanks to those who contributed...
Post by: Guest on January 08, 2005, 10:29:56 AM
Post by: Phillip_Graham on January 08, 2005, 02:00:13 PM
| Dan Mortensen wrote on Sat, 08 January 2005 03:46 |
When the PSW-6 came out, it was the first commercially available cardioid subwoofer that functioned as well as it did. At that time, I spoke with someone within Meyer (not one of the main design engineers, I believe) who explained that the method was not simply reversing polarity and adding delay, because that method would only work at one frequency, and this worked for more than two octaves. Since I don't know any better, that explanation satisfied me. |
Well, what is really more appropriate is "invert the polarity and "add" phase. When you add "pure" delay, you are really introducing a phase change that's linear with a linear change in frequency. You really want to introduce a change that's linear on an octave basis (i.e exactly half as much phase shift at 125hz as at 63hz) to keep the 1/4 wavelength spacing. The whole thing still falls apart when the interdriver spacings get too wrong, of course.
That's the essence (but not the details) of what Meyer is doing. Also, since the meyer box processed completely in the analog domain, it doesn't make sense to do pure delay.
| Quote: |
If Meyer's method is as complex as they say, and if they are proud of having the first successful commercially available product using what they figured out for the first time, I would not expect them to jump up and offer it free to anyone who would listen. |
Meyer clients, notably ultrasound, had been implementing cardiod patterns long before the days of their prepackaged products.
| Quote: |
That has nothing to do with their interest in improving the quality of audio in the industry as a whole, but, as Will said, with protecting their intellectual property. |
Except that the techniques for this kind of stuff have been published in every sonar and acoustics textbook for 40+ years. The necessary transfer functions are known, it's just implementing them that's the trick. My reference paper on this topic is from the sonar angle.
Meyer's edge here is packing it all up in a quality product that works well every night, and integrating it with all of their other processing.
If you want to talk about something where the IP side of it does matter a little more, I'd suggest EAWs DSA. There really is some innovative new science there.
Post by: KeithBroughton on January 09, 2005, 08:19:42 AM
I presume, this cardioid method is based on the fact that each cab or driver is getting the same ammount of power.
Also , I understand to get the best results, the same number of "rear" and "front" boxes should be used.
Is it safe to conclude that if half as many boxes are used for the "rear" that the result would be a reduction of the cancellation effect of 3 db?
Post by: Langston Holland on January 09, 2005, 09:15:05 PM
Post by: Langston Holland on January 09, 2005, 09:16:51 PM
Standard Array:
Cardioid Array front:
Cardioid Array side:
The following Smaart captures contain a white trace that is the 5ft high forward mic (front blue mic position), red trace that is the 5ft high rearward mic (rear blue mic position), and a green trace that is the 10ft high rearward mic (also rear blue mic position).
Bonus: (bottom 2 BH760's only, notice the 6dB front to back peak output differential and the 10dB spread around 75Hz. This is not a cardioid arrangement, just an advantage of horn subs.)
Standard 2 x 2 Array:
Cardioid 2 x 2 Array: (rear delay with polarity reversal, er... WOW)
Cardioid 2 x 2 Array: (front delay only)
Forward Outputs of each Array Compared:(White is 2 x 2 Std, Blue is 2 x 2 Front Delay, Red is 2 x 2 Rear Delay, and Green is 1 x 2 Std)
Observations:
1. Harry's right - it really works and the rear delay scenario approaches true cardioid behavior. Hearing the test signal go away at the rear was quite entertaining, but it's a shame the neighbors' homes wereon-axis to the front of the array. :))
2. Out in front of the subs, I prefer the sound of the kick with the standard or front delayed cardioid arrays. I couldn't tell the difference between them, which was as I'd hoped. The kick sounded a little softer, not just SPL, but more "rounded" - not quite as "tight" with the rear delayed cardioid array. It's likely that I would not have been able to hear this effect if I had my top cabs on.
3. What now? MUSIC! I played the kick that I recorded from my favorite local drummer with a Beta 91 and walked around the subs. Something weird happened that totally messed me up. The kick was noticeably quieter at the rear of the cardioid sub array that used the front delayed scheme. Look at those measurements - that should NOT happen - the rear delay scheme had much less measured output and sounded much quieter with the test signal. I double-checked the processor settings and reacquired a couple of measurements - same results - but that kick still refused to play fair. Then I went inside and analyzed the kick recording. Here's a representative hit:
Notice the peak in the mid-60Hz to mid-70Hz region. Now go back and look at the Smaart measurements for the two cardioid array schemes and look at the front delayed dip in this region. You can also cheat and look at the following plot where the green trace of the front delay is 3 - 8dB lower than the purple trace of the rear delay scheme. Pretty sneaky! I try to get the bass guitar to fill in the region below the kick. In that situation, the rear delay cardioid will win the day, although the bassist may wonder why the subs are "off". :)
Conclusions:
1. The measurements supported the predictions in an outdoor situation.
2. The front delayed cardioid array is for me. An amazing improvement that I have ProSoundWeb's forum to thank for. Virtually identical forward output with an eerie lack of kick "on stage". Walking around the subs at a constant radius reminded me of walking around a parked car at night with its headlights on, you were lit up only when you got in front. Parked is important. :)
3. I speculate that I would have chosen the rear delayed cardioid array if I were using caveman front-loaded subs due to my typical deployment of center sub arrays.
4. Be very careful how you interpret these results if you make your living at this. I have a feelingthat some bands are not going to believe me when I tell them the subs really work and I may have to revertto the standard array to please them. I have actually done sound for a troupe of deaf dancers that use thebass spill on stage to feel the music and move accordingly. Card sub arrays can be inappropriate - but I can't wait to start using them! :))
Post by: Phillip_Graham on January 09, 2005, 10:46:58 PM
I would suggest trying the front delay configuration with the subs stacked in a 2x2 block, two of them facing backwards, and then do the front delay. It would be easier to stack...
I gues the eventual idea for this at gigs will be two subs on the stage, and two on the ground in front? I'll have to MAPP that in the vertical plane, as I bet it provides vertical directivity, too.
Post by: Guest on January 10, 2005, 12:43:28 AM
Post by: A Man on January 10, 2005, 01:44:09 AM
A couple of questions:
* Deploying this method in a traditional L-R setup, what (possably adverse) inter-reaction would a single center sub and/or lipfills have? ie; would outer lipfills be affected by the polarity flip on the 'rear' subs?... I'm ASSuming spacing would be critical..
* Downstage lobes of the sidefills, inter-reaction with those?
* Are the Nexo CD 12/18 built internally so the elements 'line up' at the exit physically and then some degree of delay and attenuation applied?
* w/ Subs in the air...
Optimal point(s) of measurements?
Good job guys, thanks for kicking this old road dog.
Post by: KeithBroughton on January 10, 2005, 06:46:35 AM
However, in my browser , all the links show with a box with a red X in them and can't be text copied.
If I type in the addy this is the result..."Access Denied. Bandwidth limit exceeded."
Am I missing something in my browser set-up?
Post by: Chris Cowley on January 10, 2005, 07:24:27 AM
My suggestion is that the poster put them somewhere else and re-posts with the links.
Post by: Elliot Thompson on January 10, 2005, 07:31:40 AM
| Jon Martin wrote on Mon, 10 January 2005 06:44 |
This definitely has to be one of the best posts in recent memory. |
This is by far the best post the Lab has aquired since it moved from the old board!
The knowledge was always here. It was a matter of someone having the right key, opening the door, and, letting the lurkers come in!
| KeithB wrote on Mon, 10 January 2005 11:50 |
Interesting post! However, in my browser , all the links show with a box with a red X in them and can't be text copied. If I type in the addy this is the result..."Access Denied. Bandwidth limit exceeded." Am I missing something in my browser set-up? |
Dude, I'm using Mozilla Firefox, and, still have IE 5, and,they both work. So, it could be a problem on your settings.
I'm finally learning something on the Lab again!
If this is an indication on whats instore for the Lab in 2005, I'm all for it! 
Best Regards,
Post by: KeithBroughton on January 10, 2005, 07:44:09 AM
Must be my ISP.
Shazbat!
Post by: Langston Holland on January 10, 2005, 08:33:44 AM
Post by: Phillip_Graham on January 10, 2005, 09:10:16 AM
| Langston Holland wrote on Mon, 10 January 2005 08:33 |
Your browsers are fine - I had no idea so many people would read this post - I've just signed up for a "real" ftp storage account and the post should be functioning again within a couple of hours. |
It's not unreasonable to ask PSW to host those pictures for you. After all, they are hosting tons of stuff for the guys over on the recording section. You should haven't to sign up for anything to have people read your post.
PM Dave and see if he can get is stuck on the PSW server.
Post by: Chris Cowley on January 10, 2005, 12:19:10 PM
ha ha I was correct
Post by: Langston Holland on January 10, 2005, 01:54:21 PM
Turns out that the new web hosting service requires the domain name I selected to propagate to the DNS servers. Thus, I won't have the additional capacity to make the two "Measurements" posts functional until sometime tomorrow. BUT, the pictures will magically reappear at MIDNIGHT (US central time) until 33MB of bandwidth expires. The 20 pictures total about 1.5MB, thus 33/1.5 = 22 folks get to see the posts, kind of like a game show!!!
This is SILLY and I apologize. I knew almost nothing about this web/ftp stuff until this morning! :)
Post by: Langston Holland on January 10, 2005, 03:24:04 PM
Post by: KeithBroughton on January 10, 2005, 03:51:49 PM
Nice work Langston.
It's great to see the therory tested in practical terms.
Now I'm off to demonstrate this to the boss and nothers at the shop.
Thanks for all your hard work in the "field"
BIG fun!
Post by: Evan Kirkendall on January 10, 2005, 04:37:15 PM
I feel sorry for the animals in the woods of those pics. That must be a lot of sound.
Post by: Phillip_Graham on January 10, 2005, 05:41:29 PM
| Jon Martin wrote on Mon, 10 January 2005 01:44 |
This definitely has to be one of the best posts in recent memory. A couple of questions: * Deploying this method in a traditional L-R setup, what (possably adverse) inter-reaction would a single center sub and/or lipfills have? ie; would outer lipfills be affected by the polarity flip on the 'rear' subs?... I'm ASSuming spacing would be critical.. |
It's all linear addition. Put a single additional sub in the center, and it will smooth out power alley, and spill onto the stage at a level about -3dB to the front output. Make it cardiod and it will smooth the front and cancel behind.
If the lipfills are phase aligned to the subs (That Smaart note is coming, promise!), and there isn't excessive overlap of their operating bands, it shouldn't be an issue.
| Quote: |
* Downstage lobes of the sidefills, inter-reaction with those? |
Again, it's all linear sums. If you model the cardiod sub, and then add sidefill spill, it will show the same results as before plus the sidefill spill.
Careful placement of the sidefill might even let you cancel it's rear spill with the main subs, if it was at a similar wavelength spacing to the rear firing subs, and had a similar phase response (i.e. similar drivers/tuning and XO features).
You could make the sidefills cardiod, given space. It bet your monitor guy on warped tour would like that!
| Quote: |
* Are the Nexo CD 12/18 built internally so the elements 'line up' at the exit physically and then some degree of delay and attenuation applied? |
Ask Harry.
| Quote: |
* w/ Subs in the air... Optimal point(s) of measurements? |
As langston has shown, VLF response (w/ a bit of smoothing in smaart) doens't have to be taken in the ground plane, it's usually the lower mid-band response that takes a beating measurment-wise from the floor.
If you're pressed for time, only tune the system for the FOH desk!
I personally do the following on site smaart alignment scheme. This presumes the XO's for all the bandpasses in the top box are already set up properly:
1. Align the main subs to the loudest LF spill of the stage. To my mind there's no point aligning to the HF, as it's rarely coherent off the stage, and there's little chance for even summation of anything but the LF spill. I do this in the ground plane. I apply this delay on the INPUT side of the FOH DSP setup.
2. Align the subs to the low bandpass of the tops which 95% of the time involves delaying the tops. That's because the subs are usually run 6-10dB hotter than the tops, so they need an underlapped crossover to not have excessive low mid buildup. I also do this in the ground plane. I apply this delay BEFORE the input of the top box XO, or equally to all top box bandpasses.
3. Now that i have the appropriate differential delay applied to the tops, I do an impulse alignment to any delay. I usually do this with the mic at audience level, as the HF's are going to be determining the impulse arrival peak, and I'm not too worried about floor bounce effects contaminating the measurement. I apply this to the INPUT side of the delay line processing.
Note, I do the above steps via the PHASE align method if there is time, and via the IMPULSE align method if time is short.
4. Smaart the PA for eq. I will use ground plane for the lows and low mids, say <500hz, and at ear level stand for the HF's.
For something repeatable like Warped, you could have this all nailed down pretty well at the beginning. Only thing you might need to adjust would be the global INPUT delay for the stage wash, and some day to day EQ adjustments, which I would do by ear first, and only second guess myself with Smaart if there was time.
Having stuff located a foot or two in any direction relative to the last setup isn't enough to worry about to re-do all your measurements each day.
BTW, Cardiod subs would make a big difference at Warped!
Post by: Peter Morris on January 10, 2005, 08:19:41 PM
The SPL reduction behind them may not be quite as much as a true cardioid, but in many applications you don’t need it silent on stage, 10dB reduction is enough. Some musicians seem to like it loud and enjoy some of that bass that spills back, although it’s better coming from the fold-back. In a theatre or similar application it’s different of course and you wouldn’t be using 12 LABs either!
With the no delay option every thing sums correctly. With the rear delay there is summation on a continuous sin wave but not on the first transient – that’s why the kick sounded softer, (guess what Phil, you can hear it - OK -- but not much
)When you use the front delay it will sum correctly in front; this is what you heard and measured, but the rear cancellation will not be perfect, the first transient will not be cancelled, this corresponds to what you measured. Perhaps the psychoacoustics effect of this transient is why it seemed less with music than the rear delay did – don’t know.
You can also see that with the rear delay option when you reach the octave bandwidth limit of this application, things did not sum any more i.e. the 6 dB less at 30hz.
I would love to see how two blocks of BH760 in standard and cardioid mode sum in the a L-R sub placement angled out a bit to minimise the power alley with MAPP.
Anyway just want to say thanks for posting your plots and comments – great stuff.
Peter
Post by: Guest on January 11, 2005, 12:47:50 AM
Post by: Langston Holland on January 11, 2005, 09:50:55 AM
But it makes sense that you would get a widening rear cancellation bandwidth as you add more rearward subs to the array. One would have the upper hand here with front-loaded subs as you could just put them one behind the other like little indians.
My understanding at this point is that the best sub array for forward projection would be a single vertical array stacked centrally in front of the stage from floor to ceiling. 30ft or so would be ok outdoors. :)
Consider this: your idea is better than it looks on your horizontal plot because you effectively are producing a vertical stack, just laid back 90 degrees. Thus the vertical polar should show a great narrowing of output, thus keeping energy off the ceiling and efficiently directed at the audience!
The question becomes a practical matter of how to pull this off with only 10ft or so to work with from the downstage edge to the crowd barrier. It's also nice to keep the subs (and everything else) much further away than a few feet from all those beverage bearing bumble-heads (forgive the language).
I ordered 2 more BH760's last week and will be making additional measurements when I get them. I'm also scheming with the SmartStage folks on how I can get enough room under the stage to put these sub arrays. This is a front-runner at this point (front delay using 6 subs, rears stacked on boxes and almost touching the underside of the stage):
Post by: Jim Mullen on January 11, 2005, 03:11:15 PM
Post by: Jim Mullen on January 11, 2005, 03:16:07 PM
Post by: Langston Holland on January 12, 2005, 09:50:32 PM
| Harford Sound wrote on Mon, 10 January 2005 15:37 |
What is MAPP or whatever those graphs are and how do you get the results? Could you explain what everything means on them? Thanks! |
Send me a personal note if you have specific questions, but if you're looking for general advice, this is what I'd do:
1. Sign up for the back-to-back Syn-Aud-Con sound reinforcement seminars in Feb. or Apr. There is simply no excuse for missing this resource. It'll put you out about $1,500 total, which will be the best deal you'll ever get on anything in your life. It will unlock doors for you that you never knew existed. Do this before passing GO.
http://www.synaudcon.com/sched.htm
2. After you pass GO, support the industry and your brain by purchasing something like Smaart and LARA and reading every page of the manuals. You can only learn so much via books and articles, the doing of the theory is where learning really happens.
http://www.siasoft.com
http://www.integralacoustics.ca
Post by: Mike Babcock on January 12, 2005, 11:59:43 PM
| Harford Sound wrote on Mon, 10 January 2005 16:37 |
Man.. What an interesting thread. I started off reading not having a clue what was going on, but now Im starting to get it. I think Im going to have to read it a few more times to truely understand everytinhg. But I have a question. What is MAPP or whatever those graphs are and how do you get the results? Could you explain what everything means on them? Thanks! I feel sorry for the animals in the woods of those pics. That must be a lot of sound. |
Hello
MAPP is a program developed by Meyer Sound for Meyer Sound products. You place speakers in the program where they are planned to go, it will send that information to a supercomputer in CA and it will compute how those speakers will interact with each other at a specific frequency.
What you are seeing is a visual representation of SPL of a certain frequency. Since I was dealing with subs, I felt that 63Hz was appropriate. If you look at the key on the right hand side of the picture, It shows maroon (dark red) as 0 db, that is the place where 63hz is at the maximum loudness it can be. If you just look at the red areas, that is where you will find good reproduction of 63 hz. If you then look at the blue areas, that is where you will not be hearing much 63 hz. If you see streaks of blue and red, you can safely say that there will be power alley issues and those speaker boxes placed where they are at that point in time will have destructive interference in some areas. Adjusting the position, relative levels and delay times in the program can put that destructive interference in a more opportune spot.
The Cardioid Sub theory in use is basically manipulating (both position and phase) 2 or more subs so that it adds in one direction and subtracts in another.
Additionally, I did not use Meyer products for this particular show, so I picked Meyer models that were about the same vintage and polarity pattern of the speakers that I did use. It is not a perfect match, but I could figure out from my experiences with both types of speakers the difference from the program to real life.
I hope that makes things a little (a lot) clearer. If you have any additional questions, please ask.
Mike Babcock
(edit)PS: the reason behind my post was not initially to discuss cardioid subs and the theory behind it. That became a nice added part of it. The main reason was to tell everybody to learn all they can about everything audio (or lighting if you swing that way) from attending seminars and training courses. The knowlege I gained at one seminar thwarted a major problem I would not have known about until I was on the job site and I would not have even had the knowlege of how to fix it without the knowlege I gained from Mauricio and Meyer. The lab is a wonderful learning tool, and I know some didn't even know cardioid subs existed before this thread, and most probably had no clue how to deploy it. I'm not too worried about my competitors learning "tricks" from my post here, if they upgrade their service to the client, I will one up them by learning more and making my service better.
The industry as a whole needs to step up. As someone who barks and has a whole lot of trademarks
posted on a blog, (paraphrased here) Anyone can drop some money on a prepackaged system, read the manuals and call themselves a sound company. We all need to learn how and why things work.
Post by: Tom Reid on January 13, 2005, 07:42:29 AM
Thanks to everyone for raising that bar.
Post by: Stephen Robertson on January 13, 2005, 11:17:18 AM
Sorry for going OT
Stephen
Post by: Big Mig on January 14, 2005, 04:18:55 AM
MAPP plot shows one side - I'm working on how to combine this and cardioid arrays to isolate a festival or arena stage even better. Spacing was 1/4 wavelength at 100Hz between rows 1,2 and 3 with 2.5ms delay on row 2 and 5ms on the front row (no polarity swap) with physical spacing of 1/2 wavelength at 100Hz between columns. In an ideal world we'd have used 3x3.
One thing though - this technique doesn't improve the subs themselves... if I'd had access to the beasts we would now use, things would have been even more impressive.
Post by: Dr. Don on January 14, 2005, 01:12:39 PM
Thanks for starting this great thread. I'd like to add a note and a war story.
It is important to note that this only works if the sub woofers are run in their linear range. As soon as the sub woofers are driven into overload and distortion, all steering theory breaks down, and pattern control is lost. Also, remember some brands of sub woofers have non-linear distortions even when they are not operated in an overload condition so pattern control would never work.
As a war story to do with steering of low frequencies, in the early 1990’s John Meyer, Jamie Anderson, and myself experimented with steering sub woofer patterns. We (Grateful Dead) were playing large stadiums and to trying to get thorax-rattling (make your pants legs flap in the breeze) frequencies to the upper deck at the far end of the venues. We had sixteen Meyer Sound 650’s stacked on end on either side of the left/right PA stacks. That’s thirty-two eighteen-inch speakers straight up in a column on either side. Phil Lesh (the bass player) freaked and couldn't deal with the sub level on stage. In order to overcome this issue, we first decoupled the PA wings from the stage by making them free standing. That only had a minor effect, so John came up with an idea to apply some noise-canceling theory. Using a FFT analyzer, we measured the frequency response at Phil’s position on stage and stored it in the analyzer. Then we flew two 650’s in a column on either side of the stage as side fill. Next, using a phase correct parametric equalizer we exactly matched the low frequency of the side fills to the stored response of the mains. Then, while looking at the phase response, we introduced delay on the side-fill speakers until the phase traces were an exact match. Finally, we swapped the polarity of the side fills. This was a great solution, and the sub level on stage issue never raised its ugly head again.
Dr. Don (The Newbie)
Post by: Brad Harris on January 14, 2005, 04:12:47 PM
I've enjoyed reading your posts in the archives, but I'm curious as to what effects of having the bass player happy with the sub level at his position did to out in FOH?
Of was it just such an enourmous venue that it really didn't do too much detrimental effects? (I can only imagine 16 650's stacked! more-or-less one inventory of a company that I freelance for!)
Post by: Langston Holland on January 14, 2005, 04:45:10 PM
I've been very impressed with Jamie's contributions at SIA Soft - he's taught me quite a bit - you are no small legend over there as well.
On the side fill subs: I can see this working nicely for Phil and the fact that you only used 4 650's vs. the other 32 certainly prevented a material distortion of the house array. Do you remember approx. how far Phil could move around before he left his Maxwell Smart cone of silence? As you recall, Max and the Chief couldn't move very far at all. :) Were the others hammered with even more bass than before the sub side fills were flown?
Post by: Dr. Don on January 14, 2005, 07:15:00 PM
If you ask Jamie or Sam, they will both tell you we changed their lives and careers.
I have been approached to write a book, so ...
As far as the sweet spot on stage. For most musicians, especially the GD who didn't move around alot, the sweet spot was pretty well defined. Foot pedals and vocal mics were in a fixed position. The stage carpets were spiked marked so it all wound up being in the same position everyday. I personally set the carpet position with respect to the PA everyday.
Steering doesn't make sound disappear, it only moves it somewhere else. In this case, since we had steering speakers on both sides, the energy was directed off stage L & R and the sound on stage was even. Steering is basically creating interference. With such a few number of interference components, FOH was mostly uneffected.
Post by: Mike Babcock on January 14, 2005, 08:17:14 PM
Thank you for posting. Thanks for the war story. Did you actually achieve thorax-rattling in the upper decks? And how bearable was it closer up?
Since you are here and it is relevant to this discussion. Are there any plans to go forward with your training classes, as seen at http://www.drdon.com/training/index.html When? Where? How much? After the SAC grounding seminar, I'd like to put yours next on the list.
Mike
Post by: Evan Kirkendall on January 14, 2005, 08:42:00 PM
Post by: Dr. Don on January 14, 2005, 11:36:44 PM
| Quote: |
Did you actually achieve thorax-rattling in the upper decks? And how bearable was it closer up? |
Maybe some posters out there who were at some of these shows should answer this question.
Post by: Liam Flynn on January 16, 2005, 06:34:38 AM
| Dr. Don wrote on Fri, 14 January 2005 23:36 |
Did you actually achieve thorax-rattling in the upper decks? And how bearable was it closer up? Maybe some posters out there who were at some of these shows should answer this |
I attended a number of shows during this time, sat just about everywhere, and had my thorax (and more) rattled many times, during song climaxes and some very memorable drums/space moments.
Almost levitating out of your seat as the band went from whisper-quiet to full throttle and the low-end kicked in was quite an experience. A couple nights in the upper back in Hartford and the floor of Foxboro Stadium really stick out.The low-end never got unbearable, even very close. It just seemed to get bigger, fatter, and warmer. Part of that, I have thought, is that the Dead weren't a band led by the kick drum, or at least the mixes weren't. The other part, I know now, was the skill of the people at FOH, laying it on when appropriate, and knowing when to lay off as well. Knocking people over every second of every show with the kick just wasn't the point, and they knew it.
*Warning- flattery ahead*
Dr. Don, I always felt the PA was being played as another instrument at Dead shows, as a part of the experience rather than just the medium to bring the performance to the people. It was a revelation to me for the potential of SR. Dead shows stand out to me in terms of quality and dynamics like few others. The ability to bring so many people right onto the stage in an intimate way is a testament to the skills of all who made it happen. It changed the way I looked at SR. Thanks, and I feel lucky to be able to tell you in person.(Or whatever this is.)
This is an amazing thread. People have commented on it's content, comparing it to LAB of old. I'm gonna have to do some searching. Being new here, I have had plenty to read without even touching the archives.
Thanks, all.
Post by: Abdul-EQ on January 17, 2005, 12:18:21 AM
Abdul does not know a thorax, Abdul does not know a lorax.
However, Abdul has experienced a few stadium shows at that time and will testify that your sub array shook his balls. Of hashish, right out of his pocket and onto the infield. Don't know if his pants were "flapping in the wind" as was your intent because Abdul is always pantless underneath the cloak.
Now that Abdul thinks about it, he is tempted to blame you for the loss, that was some righteous shit. Ah, maybe not, the statue of limitations has probably expired.
Happy to help,
Abdul
Post by: Mike Pyle on January 28, 2005, 11:45:02 PM
| gtphill wrote on Thu, 06 January 2005 12:06 |
Actually, this a correct way of doing it. Mike B's way: You need to cancel the waves behind the front box. So (for simplicities sake) if the front box is producing cos(x) then the rear box needs to produce -cos(x + D) where D is the time it takes for the sound from the front box to reach the rear. The "-" comes from the polarity invert/box direction, and the D comes by delaying the rear box long enough from the sound from the front box to get there. Alternative way: Space the boxes 1/4 wavelength apart (90 degrees apart). Now delay the front box another 1/4 wavelength (90 degrees). The output from the the front box takes 1/4 wavelength to reach the rear box, and other 1/4 wavelength you added artificially, so cancellation ensues. The undelayed sound from the rear box takes 1/4 wavelength to get to the front box, so it sums in phase out front. Because sound diffracts around the rear box almost perfectly, it makes very little difference whether it is facing forwards or backwards, and you can't think of turning it around as a polarity inversion. Note that the second method doesn't work as well as the first, because the individual box does provide some degree of forward directivity, and there is slightly less (3dB or so) less sound behind the box than in front. This leads to a more hypercardiod-like pattern, which can be mitigated by turning down the rear sub about 3dB. But, by turning down the rear sub 3dB you lose that energy in the main lobe: |
One thing I still am not clear about:
If this array is set up like the first example you mention here, Mike B's way, is there still summation at the front of the array even though the rear sub is delayed? Or is the output of the rear sub substantially expended in cancelling the spill from the front sub?
If there is summation, how much is the sound affected by the delay in the rear sub? Is my thinking right that the combination of distance, signal delay and polarity inversion will make it a full cycle off?
Post by: Chris Davis on January 29, 2005, 12:07:01 AM
| Mike Pyle wrote on Fri, 28 January 2005 23:45 | ||
One thing I still am not clear about: If this array is set up like the first example you mention here, Mike B's way, is there still summation at the front of the array even though the rear sub is delayed? Or is the output of the rear sub substantially expended in cancelling the spill from the front sub? If there is summation, how much is the sound affected by the delay in the rear sub? Is my thinking right that the combination of distance, signal delay and polarity inversion will make it a full cycle off? |
It looks like not only the back waves get cancelled but the forward waves also get reinforced. If I am thinking correctly, the front cabs may also cancel the rear spillage from the rear cabs?
Post by: Guest on February 10, 2005, 10:32:10 PM
Post by: Guest on February 10, 2005, 10:42:48 PM
Post by: Edward Challanger on July 08, 2005, 08:38:54 AM
direct link ?
thank you
Very interesting article.
Post by: Langston Holland on April 10, 2010, 05:40:51 PM
Post by: Langston Holland on April 10, 2010, 05:42:21 PM
Standard Array:
Cardioid Array front:
Cardioid Array side:
The following Smaart captures contain a white trace that is the 5ft high forward mic (front blue mic position), red trace that is the 5ft high rearward mic (rear blue mic position), and a green trace that is the 10ft high rearward mic (also rear blue mic position).
Bonus: (bottom 2 BH760's only, notice the 6dB front to back peak output differential and the 10dB spread around 75Hz. This is not a cardioid arrangement, just an advantage of horn subs.)
Standard 2 x 2 Array:
Cardioid 2 x 2 Array: (rear delay with polarity reversal, er... WOW)
Cardioid 2 x 2 Array: (front delay only)
Forward Outputs of each Array Compared:(White is 2 x 2 Std, Blue is 2 x 2 Front Delay, Red is 2 x 2 Rear Delay, and Green is 1 x 2 Std)
Observations:
1. Harry's right - it really works and the rear delay scenario approaches true cardioid behavior. Hearing the test signal go away at the rear was quite entertaining, but it's a shame the neighbors' homes wereon-axis to the front of the array. :))
2. Out in front of the subs, I prefer the sound of the kick with the standard or front delayed cardioid arrays. I couldn't tell the difference between them, which was as I'd hoped. The kick sounded a little softer, not just SPL, but more "rounded" - not quite as "tight" with the rear delayed cardioid array. It's likely that I would not have been able to hear this effect if I had my top cabs on.
3. What now? MUSIC! I played the kick that I recorded from my favorite local drummer with a Beta 91 and walked around the subs. Something weird happened that totally messed me up. The kick was noticeably quieter at the rear of the cardioid sub array that used the front delayed scheme. Look at those measurements - that should NOT happen - the rear delay scheme had much less measured output and sounded much quieter with the test signal. I double-checked the processor settings and reacquired a couple of measurements - same results - but that kick still refused to play fair. Then I went inside and analyzed the kick recording. Here's a representative hit:
Notice the peak in the mid-60Hz to mid-70Hz region. Now go back and look at the Smaart measurements for the two cardioid array schemes and look at the front delayed dip in this region. You can also cheat and look at the following plot where the green trace of the front delay is 3 - 8dB lower than the purple trace of the rear delay scheme. Pretty sneaky! I try to get the bass guitar to fill in the region below the kick. In that situation, the rear delay cardioid will win the day, although the bassist may wonder why the subs are "off". :)
Conclusions:
1. The measurements supported the predictions in an outdoor situation.
2. The front delayed cardioid array is for me. An amazing improvement that I have ProSoundWeb's forum to thank for. Virtually identical forward output with an eerie lack of kick "on stage". Walking around the subs at a constant radius reminded me of walking around a parked car at night with its headlights on, you were lit up only when you got in front. Parked is important. :)
3. I speculate that I would have chosen the rear delayed cardioid array if I were using caveman front-loaded subs due to my typical deployment of center sub arrays.
4. Be very careful how you interpret these results if you make your living at this. I have a feelingthat some bands are not going to believe me when I tell them the subs really work and I may have to revertto the standard array to please them. I have actually done sound for a troupe of deaf dancers that use thebass spill on stage to feel the music and move accordingly. Card sub arrays can be inappropriate - but I can't wait to start using them! :))
Post by: Ed Spoto on April 10, 2010, 10:05:38 PM
Post by: David Stiles on April 11, 2010, 03:09:26 AM